A lot of modern warfare is about having the right nuggets in the right place, and getting the information needed to ensure that. Well, that would be the case if it wasn't for the "You go to war with the army you have" politicians who, of course, are always the ones invading.

But I don't want any of that.

"Modern Problems require Modern Crusaders!" said my spiritual advisor before firebombing a daycare center, and indeed, why suffer with the survivability of dragons fighting in and against modern armies when I can erase those myself by combining humanity's worst fears:

...And nerve gas

Simple really, these tiny (about a hundred micrometers?) machines live in swarms, called clusters, and hide in the shadows. They refuel and reproduce themselves through various ambient energy sources, are capable of distributed computing and perception (i.e: they piece together the larger picture from what individual bots can detect). Communication happens through either sound or electromagnetic fields.

They also paralyze and eat humans alive, leaving nothing but bones behind. As for networking, the Shadow will commit apoptosis to free up addresses every now and then.

One might say that my Shadow is overpowered. They're right.

With the sufficient kick-start (and Mephistopheles releases about 10 tons of this stuff into the atmosphere) there's no hope of eradicating it, and once enough clusters have established themselves, it will wear down mankind and erase them.

Now, I don't want that, but this thing is extremely persistent and will obliterate both morale and economy. How can I limit its power without either giving humans a chance to turn the tide or causing their demise?

In simpler terms, I want to establish an Attack on Titan Season 1 scenario. In layman's terms: humans live under the constant fear of the Shadow, but it can't get them just yet, due to some reason. How can I do that?

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    $\begingroup$ I love the idea of combining Dr. Who's Vashta Nerada with Vin Diesel's Pitch Black. Scares the b'jeebers out of me just thinking about it. But are you talking about season 1 of the show Titans? I've never seen it. And I'm going to recommend a new spiritual advisor... ๐Ÿ˜ˆ $\endgroup$
    – JBH
    Dec 22, 2020 at 0:33
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    $\begingroup$ I mean this kindly but are you sure you want the science-based tag for this question? At 100 microns, rain or a 20 kph wind would be sufficient to suppress the movement of these robots, not to mention that there's not enough fuel in something that size to propel itself appreciable distances. Nanobots have been severely oversold by SF writers. $\endgroup$ Dec 22, 2020 at 0:37
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    $\begingroup$ @GrumpyYoungMan Well, united they stand strong, and I mentioned insects for a very good reason. $\endgroup$ Dec 22, 2020 at 1:15
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    $\begingroup$ @JBH, Attack on Titan I found it a bit weak, especially when the titans turned out to be strictly diurnal yet the humans apparently take no nocturnal actions. $\endgroup$
    – Separatrix
    Dec 22, 2020 at 8:35
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    $\begingroup$ Looking to most anime as inspiration for a plot is generally an incredibly bad idea, because most of their "plots" are thinner than tissue paper. And I say this as an anime fan. $\endgroup$
    – Ian Kemp
    Dec 22, 2020 at 17:47

8 Answers 8


During the first wave of attack, most of humanity was wiped out, but not before they discovered a weapon of sorts against this "shadow that melt the flesh". The tiny units do indeed communicate using hypersonics, and it is relatively easy to disrupt their communications using a small sonic device no larger than a screwdriver.

Also, individually they aren't very powerful, so fire and glue are enough of a defense.

So now humans live in airtight communities defended by sonic barriers, where they are reasonably safe, but they can't reclaim the planet because they no longer have the tech base for building the necessary quantity of sonic emitters.

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    $\begingroup$ I like this solution because it also establishes a sense of urgency if the human's are running out of the raw materials to keep their existing emitters running $\endgroup$
    – Bitsplease
    Dec 22, 2020 at 1:04
  • $\begingroup$ This answer is for sound communication. The electromagnetic waves version is already covered by @user4574 answer. $\endgroup$
    – Rekesoft
    Dec 22, 2020 at 9:57
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    $\begingroup$ @Rekesoft I didn't want to stray too far from the idea of a protective sonic screwdriver. $\endgroup$
    – LSerni
    Dec 22, 2020 at 10:08

1. The Shadow breeds slowly.

Ten tons isn't a lot when you think on a planetary scale. That's really just enough to scare the pants off a major city. In the beginning, people will discover seemingly random killings at night, or in dark corners of subways and large building halls. Closets are NOT your friend. But like any good horror movie, the threat needs to grow just a bit slowly โ€” to make everybody really pee their pants. So, your insect-machines are quick killers, but slow replicators. It might take months or even a couple of years for this to become a planet-wide panic.

2. The Shadow needs time to reflect on the morality of what they did

Yes, they kill quickly! And they don't need anything from the humans they kill other than to lie still. But expecting the little monsters to be ready to kill again after offing an entire human being is asking a bit much! We're talking sleepy-puppy-syndrome here. Those happy bugs, once they've killed, need a day or two to recharge โ€” during which time they're moving, which means you can't trust the next shadow, either! (Yes, as machines they don't need much energy... but that's ignoring the scale of what's happening. They don't have a lot of storage capacity, either. In other words, it takes a lot of power to inject a human with nerve gas, and to replicate that nerve gas... time... it takes time....)

3. Flame throwers are cheap

Once humanity starts to get a grip on the problem (don't trust the shadows! Don't blink! Don't go out in the night! Night lights on sale at your local hardware store now! And toilet paper! Don't forget the toilet paper!) they realize that the easiest way to destroy the machines in three-dimensions is a flame thrower. If they were normal bugs pesticides would work just fine โ€” but they're not! And nothing is more satisfying than lighting up the night while cooking your most dread enemy! The only substantial problem is there are a LOT of shadows and not everything is conveniently made out of concrete. (It's OK honey, you don't need a blanket to sleep. Why's the mattress on the floor? Oh! Don't worry about that! Everybody's doing it!)

4. Which brings us to powerful magnets

The biggest problem with machines is that they suffer for magnetism. The smaller they are, the harder it is to protect them from it. Some lovely lady's walking down the street one day and happens to notice that the machines are swarming all around her, but not next to the Women's Pure Copper Healing Bracelet, $22.01 from Amazon if you Buy Now!. With her dying breath she screams out, "they hate magne...!" Suddenly everybody is wearing Neodymium magnets sewn into their clothing. But they can't use their cell phones anymore.

5. Until Bill Gates funds the development of anti-nanite nanites

And all of that gave some clever monkey enough time to both develop an anti-nanite nanite (lovingly called Warhammers! until Disney threatened a trademark infringement suit) AND pitch Bill Gates to fund their development. It's taking time to rid the planet of the monstrous machines, but it's working! The annual death rate is down to only 7% of the planetary population!

Post Script: There are some practical issues you can consider for controlling the might of your infernal machines!

(a) No shadow is completely dark, which is good for you, because the amount of light in a shadow is a convenient variable you, the author, and twiddle to balance the Terror of the Night with survivability. If you think the insects are too overpowered, lower the light level needed to occupy a shadow.

(b) As I sit here typing away I look around myself and realize that there are appreciable shadows EVERYWHERE. Not the least of which are in the space below my personal bulk. There are shadows in the creases of the plastic packaging around all the equipment. There are shadows INSIDE the equipment. Beneath books on my desk... they're everywhere. That works to your advantage, too. Your machines may have some processing power, but how do you judge an effective hiding place? That's another variable you can twiddle. If they're too overpowered, turn that knob so they hide in more and more useless shadows. Think about it, what are the odds of anyone opening up their laptop? It's just not common. But if enough of your bugs hide inside of laptops (shadows... they're everywhere) then there aren't a lot in areas that are more problematic... like under my desk where my legs are.

(c) Those little honkers will be susceptible to electromagnetic emissions (radiation-hardened insect-sized machines? Might as well admit that they're overpowered now and get it over with, right?). Humanity has massive variations in those emissions. In technology-saturated countries EM emissions are everywhere. So, here's a third dial you can twiddle โ€” making them more or less susceptible to EM. (Heaven help places that aren't saturated...)

  • $\begingroup$ Magnets + flamethrowers = small area EMP blasters. Those would be super effective at direct hits and won't violate fire safety. $\endgroup$ Dec 22, 2020 at 23:23
  • $\begingroup$ @valsaysReinstateMonica And it's really important to not violate fire safety! ๐Ÿ˜ $\endgroup$
    – JBH
    Dec 23, 2020 at 23:18

The Shadow is made of robots, so we just need to interfere the the electronics.

Humans make EMI generating posts that severely interfere with all electronics in their range. This creates a dead-zone in which the Shadow cannot pass. The posts are arranged around the perimeter of human settlements, each a few hundred meters apart. The perimeter of posts creates the electronic equivalent of a large stone wall surrounding the city.

Additional posts are placed throughout the interior of the city in a grid. These posts normally remain inactive. Occasionally some of the Shadow slip in and the extra posts will be activated to purge the city. To do this the entire city must shut down its entire electrical system. Except some hardened military equipment, any electronics left on during a purge will be destroyed.

The long term effect of multiple purges is that over the years most of the citizens have either lost use of (or given up using) most of their electronics and instead revert to a simpler way of life. Those living near the perimeters of the city were the first to give up electronics due to their proximity to the generators. The result is that the interior region has consistently remained more technologically advanced than those living on the perimeter.

Like other human electronics, the Shadow can survive the EMI if they go dormant before they are exposed. It would take too much energy to simultaneously kill the Shadow on a global scale. Also, completely flooding cities with enough interference to continually suppress the Shadow not only uses a lot of energy, but decreases the quality of life for the humans. Therefore its not done. Citizens on the perimeter might support continual suppression, but those on the interior are used to still having a modern lifestyle and strongly oppose it. What we are left with is a stalemate in which the humans can for the most part keep the Shadow out of some cities, with an occasional breach.


maybe use chemical line to disturb their perception like making them drunk or horny or repel them? (i dont know the correct english name of it)

for example using alcohol, coffee, salt, charcoal, and chalk unless this insect also can fly like mosquito or fly then adding net is a must.

something like this


enter image description here

or if human have advance enough technology they can also gene engineer or create robot insect predator as their pet to fight against them such as frog or anteater.

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    $\begingroup$ I like your answer but, just as a public safety warning, the specific brand of insecticidal chalk shown in the picture is considered unsafe: epa.gov/safepestcontrol/… $\endgroup$ Dec 22, 2020 at 0:45
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    $\begingroup$ @GrumpyYoungMan yeah i know, but that image is the one that i think help show it better regarding the insecticidal chalk when i google it. $\endgroup$
    – Li Jun
    Dec 22, 2020 at 2:52
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    $\begingroup$ @GrumpyYoungMan Well, it is miraculous deadly chalkโ€ฆ $\endgroup$
    – wizzwizz4
    Dec 22, 2020 at 17:36

Diffused lighting.

If they hide in shadows, then remove all the shadows!

Cover your buildings exterior eves with dull point lights so there are no notable shadows cast. Everything near the building is uniformly lit and shadow free. The nanities need shadow to live so cant cross void of light.

Use polished metal architecture to reflect ambient atmospheric lighting into dark alleys during the day, and reflect your street lights into a diffuse haze with no obvious shadow by putting glorified lamp shades over them.

Perhaps a white dome over the city that during the day is lit by the sun uniformly?


With tiny electronic machines you have several options

  1. high-power heating lamps, spotlights and lasers: Basically you want to heat them up from a distance, being so small they will not have a good way of dealing with thermal issues that electronics have to deal with and it works thematically by "lighting up the shadows"
  2. Electro Magnetic interference: you said they communicate with each other which means we can mess with the chosen communication avenue. If its sonic, we blast sound at them, if its laser, we blast light at them, if some other form of EM waves then we fill up that channel, even better we can try and reverse engineer their communication protocol and give them false data ("hack" them as it were). also, since they are electronic they will have extremely delicate circuitry and at those sized if would be feasible to inject faults into them by simply point a pointing a (powered) high-gain directional antenna at them.
  3. Tesla coils: This one is a little sillier but you could design a faraday-cage vehicle with a tesla coil mounted on it. Have the vehicle patrol around settlements and any swarm that gets close enough would get zapped. This solution feels pretty sci-fi and im not sure how actually feasible it is

Also there are EMPs, it is alleged that the USA has some non-nuclear EMP(usually you generate EMPs by nuking things), if it can be deployed in time then the swarm can be destroyed. The cost might be significant in destruction of infrastructure but its nothing compared to saving humans from extinction.

Personally, for a story I would use sending false signals on the swarm's frequency to make cloaking devices that render those around them "invisible" to the swarm and perhaps a human antagonist that figured out how to weaponize this cloaking to "direct" the swarm


By keeping it fragmented.

Once a nanoswarm becomes physically large enough, in terms of the number of connected nanites in that swarm, it's pretty much game over - because at that point its intelligence will exceed that of the smartest human, anything the humans have so far will be figured out and worked around, and it will be able to extrapolate how the humans will attempt to fight it in the future. It will also start to consume mass and grow exponentially, and choose to fragment itself into multiple swarms for redundancy. At that point it's well-nigh invulnerable.

So, your humans need to be actively hunting the swarms down and killing them. All the time. As in, swarm hunting is now the activity that comes next on the priority list after "eat" and "sleep". You can give your humans pretty potent stuff to do this with - EMPs on the hardware side, nasty viruses on the software side, et cetera - but they'll have to be constantly seeking out and destroying these swarms.

I'm also assuming that whoever's dropping these nanites has programmed them to go after humans only and specifically, because they want humans removed from the planet. If the depositor wants to get rid of humans and doesn't care about side-effects, they would be have a much better chance of succeeding by simply setting the nanites to endlessly self-replicate, aka gray goo.


Limited Range

Like all machines, the things can only move so far on one tank of fuel. Presumably they "refuel" from the people they eat, which is fine for towns and cities where the population is dense.

As soon as the human population gets down to a critically low density and the humans figure out that if they can run for the hills and get out of range of all of them, then they can't be reached - and a nanite that is nearly out of fuel must go into a dormant state until it detects a human near enough to reach. So the humans must never wander close to a city.

However the humans still live in fear - in the dormant state they are almost impossible to detect, being so small, and the robots can easily detect the humans first, or that they are intelligent enough that they can hop onto a moving object (e.g. a bird or a wild animal) in the "hope" that they will be carried to another human colony.


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